1. Field of the Invention
The invention relates to optical equipment, more particularly to a lens device that can operate precisely during zoom adjustment.
2. Description of the Related Art
As shown in FIG. 1, a conventional lens device includes a base 1, a stationary barrel component 2 mounted to the base 1, a rotatable barrel component 3 sleeved rotatably on the stationary barrel component 2, a first lens unit 4 extending into the stationary barrel component 2, a second lens unit 5, a third lens unit 6, and an anti-slip component 7 disposed between the stationary barrel component 2 and the rotatable barrel component 3.
The stationary barrel component 2 is mounted to the base 1 through a plurality of screws 201 (only one is shown), and has an inner barrel surface 203 that surrounds an axis (K) and that defines an inner space 202, an outer barrel surface 204 that is disposed opposite to the inner barrel surface 203 in radial directions relative to the axis (K), and a stop flange 206 that is disposed opposite to the base 1 along the axis (K) and that extends radially and outwardly from the outer barrel surface 204. The stationary barrel component 2 is formed with a plurality of elongated slots 205 that extend through the inner and outer barrel surfaces 203, 204, and that extend parallel to the axis (K). The rotatable barrel component 3 has an annular inner surface 301 that confronts the outer barrel surface 204 of the stationary barrel component 2. The rotatable barrel component 3 is formed with a plurality of first cam slots 302 that correspond respectively in position to the elongated slots 205 in the stationary barrel component 2 and that extend around the axis (K), and a plurality of second cam slots 303 that are staggered relative to the first cam slots 302 and that also correspond respectively in position to the elongated slots 205. The first lens unit 4 extends into the inner space 202 in the stationary barrel component 2, is movable relative to the third lens unit 6 along the axis (K), and includes a first lens barrel 401 and a first lens 402 that is disposed in the first lens barrel 401. The first lens barrel 401 has a plurality of first guide pins 403 that extend through the elongated slots 205 in the stationary barrel component 2, and that are guided by the first cam slots 302 in the rotatable barrel component 3. The second lens unit 5 is disposed in the inner space 202 in the stationary barrel component 2, is also movable relative to the third lens unit 6 along the axis (K), and includes a second lens barrel 501 and a second lens 502 that is disposed in the second lens barrel 501. The second lens barrel 501 has a plurality of second guide pins 503 that extend through the elongated slots 205 in the stationary barrel component 2, and that are guided by the second cam slots 303 in the rotatable barrel component 3. The anti-slip component 7, such as an annular piece of flock paper, can position the rotatable barrel component 3 relative to the stationary barrel component 2 through friction. When the rotatable barrel component 3 rotates, it will drive the first and second lens units 4, 5 to move relative to the third lens unit 6, thereby resulting in zoom adjustment for the conventional lens device.
The rotatable barrel component 3 is positioned relative to the stationary barrel component 2 along the axis (K) through the base 1 and the stop flange 206 of the stationary barrel component 2. In order for the rotatable barrel component 3 to rotate smoothly relative to the stationary barrel component 2, there is a gap 8 formed between the stop flange 206 and a radial end face of the rotatable barrel component 3 that confronts the stop flange 206. However, the gap 8 also provides room for the rotatable barrel component 3 to be movable along the axis (K) while rotating. Therefore, the first and second lens units 4, 5 driven by the rotatable barrel component 3 are not able to move precisely during zoom adjustment. Moreover, axial movement of the rotatable barrel component 3 while rotating will result in an image shaking effect.
In addition, the anti-slip component 7 is disposed in order to increase the friction between the stationary barrel component 2 and the rotatable barrel component 3, and to eliminate the image shaking effect. However, installation of the anti-slip component 7 results in a relatively long manufacturing time and a relatively high manufacturing cost. Moreover, since the anti-slip component 7 is made of flock paper, flocks thereof may fall off, thereby resulting in an unstable quality for the conventional lens device.